Sorting values with condition in a dataframe

Question

I would like to sort the col2 in descending order based on col1. I have the feeling that the answer is very simple, but I can't find a correct way. I would appreciate a lot some help.

The dataframe looks like:

Col1 Col2 Col3 
AB   5    Blue
AB   1    Red
AB   2    Green
AC   1    Red
AC   4    Blue
AD   9    Red
AD   5    Blue
AD   7    Green

The desired output:

Col1 Col2 Col3 
 AB   5    Blue
 AB   2    Green
 AB   1    Red
 AC   4    Blue
 AC   1    Red
 AD   9    Red
 AD   7    Green
 AD   5    Blue

What I tried:

df = pd.read_csv('data.csv')
df.sort_values(['Col1','Col2'], ascending = False)

df.groupby(['Col1'])['Col2'].sort_values(ascending = False)

None of the above methods gives the desired output.

Dani Mesejo · Accepted Answer · 2019-11-18 20:56:52Z

2

Do:

print(df.sort_values(['Col1', 'Col2'], ascending=[True, False]))

Output

  Col1  Col2   Col3
0   AB     5   Blue
2   AB     2  Green
1   AB     1    Red
4   AC     4   Blue
3   AC     1    Red
5   AD     9    Red
7   AD     7  Green
6   AD     5   Blue

From the documentation on sort_values:

ascending : bool or list of bool, default True

Sort ascending vs. descending. Specify list for multiple sort orders. If this is a list of bools, must match the length of the by.

answered Nov 18, 2019 at 20:56

Dani Mesejo

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